Antipollution apparatus for motor vehicle engines

ABSTRACT

With a view to the decrease in the production of such noxious exhaust gases as nitrogen oxides and hydrocarbons by a motor vehicle gasoline engine, an antipollution apparatus is provided for combined use with the ignition advancing mechanism of the vehicle engine which advances its spark timing by utilizing a variable degree of vacuum created adjacent the carburetor outlet in accordance with throttle opening. The antipollution apparatus is composed essentially of a dual diaphragm valve to be affixed to the intake manifold in a position adjacent its entrance, with the ignition advancing mechanism communicated with the carburetor via the valve. The pair of spaced-apart diaphragms of this valve deflects simultaneously in response to a prescribed degree of vacuum building up within the intake manifold as when the vehicle is cruising, thereby permitting the inflow of atmospheric air into the passageway between the carburetor and the ignition advancing mechanism. The ignition advance which has been caused by the latter is thus canceled each time the load on the engine decreases to the prescribed level.

United States Patent 1 Hayashi Oct. 21, 1975 ANTIPOLLUTION APPARATUS FOR MOTOR VEHICLE ENGINES [75] Inventor: Mikio Hayashi, Tokyo, Japan [73] Assignee: Hayashi Seiko Kabushiki Kaisha,

Tokyo, Japan [22] Filed: Feb. 6, 1974 [21] Appl. No.: 440,258

30 Foreign Application Priority Data Feb. 9, 1973 Japan 48-15693 [52] US. Cl. 123/117 A; 123/97 B [51] Int. Cl. F02P 5/04 [58] Field of Search 123/117 A; 200/83; 92/98 [56] References Cited UNITED STATES PATENTS 2,039,717 5/1936 Hueber 200/83 3,081,793 3/1963 Flatt 123/117 A 3,356,083 12/1967 Clark 123/117 A 3,545,070 12/1970 Bauer 92/98 3,572,301 3/1971 Kalippke.... 123/117 A 3,599,614 8/1971 Kittredge 123/117 A 3,677,238 7/1972 Harada 123/117 A Primary Examiner-Charles J. Myhre Assistant Examiner-Ronald B. Cox Attorney, Agent, or FirmMarshall & Yeasting [57] ABSTRACT With a view to the decrease in the production of such noxious exhaust gases as nitrogen oxides and hydrocarbons by a motor vehicle gasoline engine, an antipollution apparatus is provided for combined use with the ignition advancing mechanism of the vehicle engine which advances its spark timing by utilizing a variable degree of vacuum created adjacent the carburetor outlet in accordance with throttle opening. The antipollution apparatus is composed essentially of a dual diaphragm valve to be affixed to the intake manifold in a position adjacent its entrance, with the ignition advancing mechanism communicated with the carburetor via the valve. The pair of spaced-apart diaphragms of this valve deflects simultaneously in response to a prescribed. degree of vacuum building up within the intake manifold as when the vehicle is cruising, thereby permitting the inflow of atmospheric air into the passageway between the. carburetor and the ignition advancing mechanism. The ignition advance which has been caused by the latter is thus canceled each time the load on the engine decreases to the prescribed level.

7 Claims, 5 Drawing Figures US. Patent Oct. 21, 1975 Sheet 1 of3 3,913,540

' US. Patent Oct. 21, 1975 Sheet 2 of 3 3,913,540

US. Patent 0a. 21, 1975 Sheet 3 of3 3,913,540

5 238% 382% $5 7: 00m cow 00m 00m 0Q EHONV MNVHD :30 8338936 'DNIWIL NOILINOI ANTIPOLLUTION APPARATUS FOR MOTOR VEHICLE ENGINES BACKGROUND OF THE INVENTION This invention relates to antipollution apparatus for particular use with the reciprocating piston-type gasoline engines of motor vehicles.

Of the various noxious gases exhausted by conventional motor vehicle gasoline engines, hydrocarbons and carbon monoxide can be reduced significantly through proper carburetion of the fuel and air. However, nitrogen oxides also included in the exhaust products of the vehicle engines are not produced through the same chemical mechanism as hydrocarbons or carbon monoxide but, indeed, through a completely different mechanism from carbon monoxide in particular. It is therefore necessary that the exact causes for the production of these noxious exhaust gases be ascertained and remedied individually to minimize air pollution.

As is well known the production of nitrogen oxides and hydrocarbons by the vehicle engines can be reduced substantially by suitably retarding their ignition timing. However, this method usually results also in the decreased power output and ready overheating of the engines, thereby impairing fuel economy and vehicle performance. With a view to circumventing such drawbacks it has recently been proposed in the United States to retard the ignition timing greatly during engine idling and to cancel the ignition retard automatically when the engine has sufficiently increased its speed or has overheated. Another similar scheme has also been developed in which the engine is preset to have an ignition retard of from about 5 to 6 of crank angle, such that the preset ignition retard is canceled automatically only upon engine overheating.

These known schemes have serious disadvantages in common in connection with engine overheating, arising fundamentally from the great ignition retard during engine idling. The heat production of the engines operating on the bases of such schemes is so excessive that the devices for canceling the ignition retard are required to operate for prolonged lengths of time until the overheating ceases. It will be apparent that motor vehicles powered by such engines are highly unsatisfactory, especially on the streets of urban areas.

SUMMARY OF THE INVENTION It is therefore an object of this invention to provide an antipollution apparatus whereby the production of noxious exhaust gases by motor vehicle gasoline engines, notably nitrogen oxides and hydrocarbons, can be reduced significantly without any substantial adverse effects upon engine performance.

Another object of the invention is to provide an antipollution apparatus of highly compact, simple and inexpensive construction, such that it can be easily incorporated in a conventional motor vehicle gasoline engine without any substantial modification of its existing parts.

With these objects in view and the other objects hereinafter set forth, this invention provides an antipollution apparatus for use in combination with the known ignition advancing mechanism of a motor vehicle gasoline engine which advances its ignition timing by utilizing a variable degree of vacuum created adjacent the carburetor outlet in step with throttle opening. The antipollution apparatus according to the invention consists essentially of a dual diaphragm valve having a housing the interior of which is partitioned by a pair of spaced-apart diaphragms into first, second and third chambers. The first chamber communicates with the interior of the intake manifold. The second chamber between the diaphragms communicates with the atmosphere. The third chamber is subdivided into a first section through which the ignition advancing mechanism communicates with the interior of the carburetor at a point adjacent its throttle valve and a second section communicating with the atmosphere. Hence, as a prescribed degree of vacuum builds up within the intake manifold, the pair of diaphragms are caused simultaneously to deflect by suction exerted through the first chamber, thereby intercommunicating the first and second sections of the third chamber and thus canceling the ignition advance which has been caused by the ignition advancing mechanism.

According to more specific aspects of the invention the functioning of the ignition advancing mechanism is nullified in the above described fashion when the intake manifold vacuum becomes about 300 mm Hg. This degree of vacuum is reached only upon decrease in the load on the engine, as when the vehicle is running at constant speed. With the vehicle in cruising condition the engine is usually required to deliver only less than half as much power output as when the vehicle is accelerating. It is therefore most desirable to cancel the ignition advance at this time, the resultantly lowered combustion temperature of the engine being effective to reduce the production of nitrogen oxides, among other exhaust gases.

Should the ignition advance be canceled when the vehicle is accelerating, the period of time required for the vehicle to complete thedesired acceleration would become longer due to the decreased power output of the engine. Hence the overall amount of nitrogen oxides and other gases exhausted throughout this prolonged length of time would increase rather than decrease. For this reason the functioning of the ignition advancing mechanism is not nullified during vehicle acceleration according to the concepts of this invention, although it may be nullified toward the end of each accelerating period when the engine is greatly relieved of its load.

In the use of the antipollution apparatus according to the invention the engine may be preset to have an ignition retard of only up to about 3 in order to prevent engine overheating during idling and to secure sufficient power output at the start of acceleration. In this manner the invention will contribute in no small measure toward prevention of air pollution especially in urban areas.

The features which are believed to be novel and characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and mode of operation, together with the further objects and advantages thereof, will be best understood from the following description taken in conjunction with the accompanying drawings which illustrate, by way of example only, a preferred embodiment of the invention and in which like reference numerals denote like parts of the several views.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:

FIG. 1 is a partly broken away sectional view showing the overall arrangement of antipollution apparatus according to the principles of this invention;

FIG. 2 is an enlarged left hand side elevational view of the dual diaphragm valve in the arrangement of FIG.

FIG. 3 is an enlarged right hand side elevational view of the dual diaphragm valve in the arrangement of FIG.

FIG. 4 is an axial sectional view of the dual diaphragm valve, the view being explanatory of the operation of the antipollution apparatus according to the invention; and

FIG. 5 is a graph plotting the curves of ignition timing against various degrees of intake manifold vacuum according to the invention and to the prior art.

DESCRIPTION OF THE PREFERRED EMBODIMENT The principles of this invention are perhaps best embodied in the arrangement of FIG. 1, which includes an antipollution device according to the invention, an intake manifold 11 of the motor vehicle gasoline engine, a carburetor 12, an air cleaner 13, and an ignition advancing mechanism 14.

The antipollution device 10 is essentially a dual diaphragm valve having a housing 15 of hollow, substantially cylindrical shape which in practice may be hexagonal or otherwise polygonal in cross sectional shape as shown in FIGS. 2 and 3. The housing 15 includes a reduced diameter portion 16 at its right hand end, as viewed in FIG. 1, and an externally screw threaded, hollow neck 17 extends axially outwardly therefrom. The neck 17 is adapted to be screwed into a correspondingly internally screw threaded bore formed in the wall of the intake manifold 1 1 adjacent its entrance, thereby securely to mount the antipollution device 10 in position and further to communicate the interior of the housing 15 with the interior of the intake manifold 11 via the axial bore of the neck 17.

The interior of the housing 15 is pressure-tightly divided by a pair of spaced-apart diaphragms 18 and 19 of hard rubber or like material into a first chamber 20 seen to the right in FIG. 1 which is in open communication with the interior of the intake manifold 11, a second or intermediate chamber 21, and a third chamber 22 to the left. An annular spacer 23 is closely fitted against the inside surface of the housing 15 between the diaphragms l8 and 19, and another spacer 24 which may be cylindrical in shape is disposed centrally therebetween. A passageway 25 is formed through the housing 15 and the first mentioned spacer 23 to communicate the second chamber 21 with the atmosphere.

Within the third chamber 22 an annular retainer 26 is likewise closely fitted against the inside surface of the housing 15 to retain the diaphragms l8 and 19 undisplaceably in their respective desired positions within the housing. Preferably, the inside diameter of this annular retainer 26 should be reduced at its end adjacent to the diaphragm 19 as shown in FIG. 1, for purposes hereinafter referred to.

The left hand end of the housing 15 is pressuretightly closed by a cover 27. A partition 28 of hollow cylindrical shape, which is open at its right hand end, is formed substantially integral with the cover 27 and is disposed axially within the third chamber 22 to subdivide the same into an annular outside section and an inside section located centrally thereof. It may be noted that a suitable spacing exists between the right hand end of the annular retainer 26, where it is reduced in inside diameter as above mentioned, and the partition 28.

Within the first chamber 20 a pair of spring supports are provided'at 29 and 30 to support a helical compression spring 31 therebetween. The diaphragm 19 is thus yieldably urged into pressure tight contact with the open right hand end of the partition 28 via the diaphragm 18 and the spacer 24. The diaphragm 18 and 19 together with the spacer 24 and the spring support 30 are united together as by means of a rivet 32. Hence, as a prescribed degree of vacuum builds up within the intake manifold l 1 during operation of the motor vehicle engine, the diaphragms 18 and 19 will deflect simultaneously against the force of the compression spring 31 due to suction exerted through the hollow neck 17, thereby intercommunicating the internal and external spaces of the partition 28 within the third chamber 22.

It is further possible according to the invention to vary in a controllable manner the intake manifold vacuum at which the diaphragms 18 and 19 are caused to deflect as above stated. There is provided to this end an adjusting rod 33 externally screw threaded to mesh with corresponding internal screw threads formed in the axial bore of the neck 17 of the housing 15. The adjusting rod 33 is also bored axially therethrough and has its left hand end coupled to the spring support 29. Hence, prior to the mounting of the antipollution device 10 in position as shown in FIG. 1, the adjusting rod 33 may be turned relative to the housing 15 as by a screwdriver fitted in a groove 34, FIG. 3, formed diametrically at its exposed end, thereby adjusting the initial tension of the helical compression spring 31 to a desired value.

The aforesaid cover 27 closing the left hand end of the housing 15 has three ports 35, 36 and 37 therethrough which can be aligned diametrically of the cover as shown in FIGS. 1 and 2. The ports 35 and 37 are thus both open to the external space of the partition 28 within the third chamber 22, whereas the port 36 is open to the internal space of the partition 28. The port 35 communicates via a conduit 38 with a port 39 open to the interior of the carburetor 12 in a position adjacent its throttle valve 40. The port 36 communicates via a conduit 41 with the interior of a casing 42 of the air cleaner 13 or with the atmosphere. The port 37 communicates via a conduit 43 with a vacuum chamber 44 of the ignition advancing mechanism 14. The conduits 38, 41 and 43 can all be in the form of hoses of rubber or like material connected at both ends to fittings 45 and 46, 47 and 48, and 49 and 50, respectively.

The carburetor 12 is rigidly connected to the intake manifold 11 as shown in FIG. 1, and the air cleaner case 42 containing a filtering element 51 and closed by a cover 52 at its top is mounted upon the carburetor 12 as by a bolt 53. It is to be noted, however, that such arrangement of the intake manifold 1 l, the carburetor l2 and the air cleaner 13 is conventional and does not, by itself, constitute a part of this invention. Other types of such engine components may be adopted without necessarily prejudicing the novelty of the invention.

While the ignition advancing mechanism 14 has also been well known and does not by itself constitute a part of this invention, its configuration may be briefly explained as follows. The interior of a casing 54 is partitioned by a diaphragm 55 into the vacuum chamber 44 and an atmospheric pressure chamber 56. The diaphragm 55 is secured to one end of an actuating rod 57 which extends through the atmospheric pressure chamber 56 and has its other end projecting out of the casing 54. A helical compression spring 58 is mounted in the vacuum chamber 44 to maintain yieldably the diaphragm 55 in its normal position. The ignition advancing mechanism 14 as a whole constitutes a substantial part of the distributor, not shown, of the motor vehicle engine, such that the actuating rod 57 moves back and forth with the diaphragm 55 in accordance with a variable degree of vacuum created in the vacuum chamber 44 thereby causing the distributor to vary the ignition timing in the known manner.

Proceeding to the description of the operation of this preferred embodiment of the invention, it should be first noted that when the throttle valve 40 is opened in the operation of the motor vehicle engine, suction may be exerted on the diaphragm 55 of the ignition advancing mechanism 14 via the port 39, the conduit 38, the port 35, the external space of the partition 28 within the third chamber 22, the port 37, the conduit 43, and the vacuum chamber 44. The ignition advancing mechanism 14 is thus caused to operate to advance the spark timing as required in accordance with the prior art.

It will be apparent that the intake manifold vacuum rises with the decrease in the load on the engine taking place as when the vehicle is running at constant speed. Thus, when the intake manifold vacuum reaches a preselected value of, say, about 300 mm Hg, the diaphragms 18 and 19 are caused to deflect simultaneously against the force of the compression spring 31 by suction exerted through the axial bore of the adjusting rod 33 as will be understood from FIG. 4. The diaphragm 19 thus moves out of contact with the partition 28 thereby permitting the inflow of the filtered atmospheric air from the air cleaner 13 into the external space of the partition within the third chamber 22 via the conduit 41 and the port 36. As a consequence the pressure in the external space of the partition 28 within the third chamber 22, which has been held negative to exert suction upon the diaphragm 55 of the ignition advancing mechanism 14, rapidly rises to the atmospheric pressure to terminate its operation. The ignition advance which has been caused by the mechanism 14 is thus canceled completely.

Such operation of the prior art ignition advancing mechanism 14 and of the antipollution apparatus according to this invention will be apparent from the graph of FIG. 5, in which the curve 0 represents the change in ignition timing according to the prior art and the curve b the corresponding change in ignition timing according to the invention. It has been confirmed by experiments that in general, the decrease in the production of nitrogen oxides at various intake manifold pressures thanks to the provision of the antipollution device according to the invention roughly corresponds to the differences cl, c2 and so forth between the corresponding values of the curves a and b. The dif ference cl comes from the present ignition retard of up to about 3 according to the invention.

According to performance tests conducted by an independent institute, a motor vehicle with its engine equipped with the antipollution apparatus of the invention exhibited a 10% decrease in the production of hydrocarbons and a 48% decrease in the production of nitrogen oxides as it ran on a substantially level road at a constant speed of 40 kilometers per hour.

The use of the dual diaphragm valve as herein disclosed is essential to derive the full benefits out of the antipollution apparatus according to the invention. It will be seen that the suction exerted on the respective diaphragms 18 and 19 of the valve by a given degree of vacuum is proportional to their effective surface area. The effective surface area of the diaphragm 18 can be expressed as the area of a circle whose diameter is equal to the diameter of the first chamber 20, and that of the diaphragm 19 as the area of a circle whose diameter is equal to the minimum inside diameter of the retainer 26 minus the area of a circle whose diameter is equal to the outside diameter of the partition 28. The effective surface area of the diaphragm 18 is much greater than that of thediaphragm 19.

Assume, for the purpose of comparison, that the diaphragm 18 and the passageway 25 are not provided in this valve. Then the effective surface area of the remaining diaphragm 19 with respect to the suction caused by the intake manifold vacuum is equal to the area of a circle whose diameter is equal to the minimum inside diameter of the retainer 26. Since the external space of the partition 28 within the third chamber 22 is held negative when out of communication with the internal space of the partition, the actual effective surface area of the diaphragm can be considered equal to the area of a circle whose diameter is equal to the inside diameter of the partition 28.

As will be apparent from the foregoing, the provision of the two spaced-apart diaphragms 18 and 19 with the atmospheric chamber 21 therebetween makes it easier for the suction by the intake manifold vacuum to overcome the suction by the throttle valve vacuum. It will therefore be appreciated that the dual diaphragm valve according to the invention is far more responsive to changes in the degree of intake manifold vacuum than the single diaphragm valve.

While this invention has been shown and described hereinbefore in terms of a preferred embodiment thereof, it is to be understood that the invention is not to be restricted by the exact showing of the drawings or the description thereof. For example, the antipollution device 10 may not necessarily be affixed directly to the intake manifold but may be mounted in any other convenient location with its first chamber 20 communicated with the interior of the intake manifold via a conduit. It will also be apparent that if required, the diaphragms 18 and 19 can be caused to deflect at intake manifold pressure other than about 300 mm Hg by the manipulation of the adjusting rod 33.

Thus, a latitude of modification, substitution and change is intended in the foreging disclosure, and in some instances some features of the invention may be employed without the corresponding use of other features. It is therefore appropriate that the invention be construed broadly and in a manner consistent with the spirit and scope of the invention as sought to be defined by the following claims.

I claim:

1. In combination with an ignition advancing mechanism of a motor vehicle gasoline engine comprising a casing, a diaphragm dividing the interior of said casing into a vacuum chamber and an atmospheric pressure chamber, and an actuating rod having one end coupled to said diaphragm and the other end projecting out of said casing via said atmospheric pressure chamber, said actuating rod being adapted to cause the distributor of the motor vehicle engine to advance the ignition timing in response to a variable degree of vacuum created in said vacuum chamber, an antipollution apparatus comprising:

a housing substantially in the shape of a hollow cylinder;

a pair of spaced-apart diaphragms within said housing pressure-tightly dividing the interior thereof into:

a first chamber adjacent one end of said housing which communicates with the interior of the intake manifold of the motor vehicle engine;

a second chamber intermediate both ends of said housing which communicates with the atmosphere; and

a third chamber adjacent the other end of said housing;

means interconnecting said pair of diaphragms in spaced-apart relationship;

partition means fixedly mounted in said third chamber and pressure-tightly subdividing the same into first and second sections, said partition means being normally held in pressure-tight contact with one of said pair of diaphragms to hold said first and second sections out of communication from each other;

means communicating said first section of said third chamber with the interior of the carburetor of the motor vehicle engine at a point adjacent its throttle valve;

means further communicating said first section of said third chamber with said vacuum chamber of said ignition advancing mechanism; and

means communicating said second section of said third chamber with the atmosphere;

whereby when a prescribed degree of vacuum builds up within said intake manifold during operation of the motor vehicle engine, said pair of diaphragms are caused to deflect simultaneously by suction exerted through said first chamber, thereby intercommunicating said first and second sections of said third chamber and hence nullifying the ignition advance which has been caused by said ignition advancingmechanism.

2. The antipollution apparatus as recited in claim 1, including a hollow neck extending axially outwardly from said one end of said housing, said hollow neck being adapted to be screwthreadedly received in a bore formed through the wall of said intake manifold in order to support said housing in position and further to communicate said first chamber with the interior of said intake manifold therethrough.

3. The antipollution apparatus as recited in claim 2, including a helical compression spring in said first chamber yieldably urging said pair of diaphragms toward said other end of said housing in order normally to hold said one diaphragm in pressure-tight contact with said partition means.

4. The antipollution apparatus as recited in claim 3, including means for controllably varying the intake manifold pressure at which said pair of diaphragms are caused to deflect to intercommunicate said first and second sections of said third chamber, said varying means including a hollow adjusting rod screw-threadedly received in said hollow neck of said housing, said adjusting rod having one end projecting into said first chamber to engage one end of said helical compression spring, whereby the initial tension of said helical compression spring can be adjusted to a desired value by revolving said adjusting rod relative to said hollow neck.

5. The antipollution apparatus as recited in claim 1, wherein said partition means is in the shape of a hollow cylinder disposed in coaxial relationship to said housing and having one end closed by said other end of said housing and the other and normally held in pressuretight contact wit said one diaphragm, said first and second sections being located externally and internally of said hollow cylinder, respectively.

6. The antipollution apparatus as recited in claim 1, wherein said second section of said third chamber communicates with the interior of the air cleaner case of the motor vehicle engine.

7. The antipollution apparatus as recited in claim 1, wherein said prescribed degree of vacuum within said intake manifold is about 300 mm Hg. 

1. In combination with an ignition advancing mechanism of a motor vehicle gasoline engine comprising a casing, a diaphragm dividing the interior of said casing into a vacuum chamber and an atmospheric pressure chamber, and an actuating rod having one end coupled to said diaphragm and the other end projecting out of said casing via said atmospheric pressure chamber, said actuating rod being adapted to cause the distributor of the motor vehicle engine to advance the ignition timing in response to a variable degree of vacuum created in said vacuum chamber, an antipollution apparatus comprising: a housing substantially in the shape of a hollow cylinder; a pair of spaced-apart diaphragms within said housing pressuretightly dividing the interior thereof into: a first chamber adjacent one end of said housing which communicates with the interior of the intake manifold of the motor vehicle engine; a second chamber intermediate both ends of said housing which communicates with the atmosphere; and a third chamber adjacent the other end of said housing; means interconnecting said pair of diaphragms in spaced-apart relationship; partition means fixedly mounted in said third chamber and pressure-tightly subdividing the same into first and second sections, said partition means being normally held in pressuretight contact with one of said pair of diaphragms to hold said first and second sections out of communication from each other; means communicating said first section of said third chamber with the interior of the carburetor of the motor vehicle engine at a point adjacent its throttle valve; means further communicating said first section of said third chamber with said vacuum chamber of said ignition advancing mechanism; and means communicating said second section of said third chamber with the atmosphere; whereby when a prescribed degree of vacuum builds up within said intake manifold during operation of the motor vehicle engine, said pair of diaphragms are caused to deflect simultaneously by suction exerted Through said first chamber, thereby intercommunicating said first and second sections of said third chamber and hence nullifying the ignition advance which has been caused by said ignition advancing mechanism.
 2. The antipollution apparatus as recited in claim 1, including a hollow neck extending axially outwardly from said one end of said housing, said hollow neck being adapted to be screwthreadedly received in a bore formed through the wall of said intake manifold in order to support said housing in position and further to communicate said first chamber with the interior of said intake manifold therethrough.
 3. The antipollution apparatus as recited in claim 2, including a helical compression spring in said first chamber yieldably urging said pair of diaphragms toward said other end of said housing in order normally to hold said one diaphragm in pressure-tight contact with said partition means.
 4. The antipollution apparatus as recited in claim 3, including means for controllably varying the intake manifold pressure at which said pair of diaphragms are caused to deflect to intercommunicate said first and second sections of said third chamber, said varying means including a hollow adjusting rod screwthreadedly received in said hollow neck of said housing, said adjusting rod having one end projecting into said first chamber to engage one end of said helical compression spring, whereby the initial tension of said helical compression spring can be adjusted to a desired value by revolving said adjusting rod relative to said hollow neck.
 5. The antipollution apparatus as recited in claim 1, wherein said partition means is in the shape of a hollow cylinder disposed in coaxial relationship to said housing and having one end closed by said other end of said housing and the other and normally held in pressure-tight contact wit said one diaphragm, said first and second sections being located externally and internally of said hollow cylinder, respectively.
 6. The antipollution apparatus as recited in claim 1, wherein said second section of said third chamber communicates with the interior of the air cleaner case of the motor vehicle engine.
 7. The antipollution apparatus as recited in claim 1, wherein said prescribed degree of vacuum within said intake manifold is about 300 mm Hg. 